1 % ^ STATE  OF  ILLINOIS 


STATE  HIGHWAY  DEPARTMENT 


BULLETIN  NO.  13 


The  Testing  of  Road  Oils 

Including  Character  of  Oils  and  Methods 
of  Examination. 


Prepared  by 

F.  L.  ROMAN 

Testing  Engineer,  Illinois  State  Highway  Department 


£ ' f t 1 '■ 

Springfield,  Illinois,  December,  1916 


[Printed  by  authority  of  the  State  of  Illinois.] 


STATE  OF  ILLINOIS 


STATE  HIGHWAY  DEPARTMENT 


BULLETIN  NO.  13 


The  Testing  of  Road  Oils 

Prepared  by 

F.  L.  ROMAN 

Testing  Engineer,  Illinois  State  Highway  Department 


COMMISSION. 

A.  D.  Gash,  President. 
S.  E.  Bradt,  Secretary. 
James  P.  Wilson. 


Wm.  W.  Marr,  Chief  State  Highway  Engineer. 


BUREAU  CHIEFS. 
Clifford  Older,  Bridge  Engineer. 

H.  E.  Bilger,  Road  Engineer. 

B.  H.  Piepmeier,  Maintenance  Engineer. 
F.  L.  Roman,  Testing  Engineer. 

J.  M.  McCoy,  Chief  Clerk. 


Springfield,  Illinois. 
December,  1916. 


Schnepp  & Barnes,  State  Printers 
Springfield,  III. 

1917. 


P5543 — 1M 


CONTENTS. 


PAGE. 

Preface  5 

Introduction  7 

Source  and  Character  of  Road  Oils 7 

Chemical  Composition  of  Road  Oils 8 

Methods  of  Testing 10 

Specific  Gravity  10 

Specific  Viscosity  13 

Volatilization  Loss  16 

Solid  Risidue  19 

Flash  and  Burning  Points 21 

Total  Bitumen  23 

Bitumen  Insoluble  in  Paraffin  Naphtha 25 

Fixed  Carbon  26 

Paraffin  Scale  27 

Miscellaneous  Tests  29' 

References  29 


ILLUSTRATIONS. 


PAGE. 

Westphal  Balance,  Figure  1 12 

Hydrometer,  Figure  2 12 

Pycnometer,  Figure  3 12 

Engler  Viscosimeter,  Figure  4 14 

New  York  Testing  Laboratory  Oven,  Figure  5 17 

Dow  Penetration  Machine,  Figure  6 19 

Open  Cup  Oil  Tester,  Figure  7 22 

Apparatus  for  Determining  Soluble  Bitumen,  Figure  8 24 

Apparatus  for  Determining  Fixed  Carbon,  Figure  9 24 

Freezing  Apparatus  for  Determining  Paraffin  Scale,  Figure  10 28 


PREFACE. 


The  increasing  use  of  road  oils  in  highway  work,  especially  in 
the  surface  treatment  of  earth  roads,  has  made  it  necessary  for  high- 
way engineers  and  road  oil  manufacturers  to  have  a clear  under- 
standing of  the  specifications  involved,  and  consequently  of  the 
nature  and  character  of  these  oils  and  of  the  methods  of  testing. 
Jn  preparing  the  following  treatise,  an  effort  has  been  made  to 
give  this  information  in  readily  available  form.  This  bulletin  is 
necessarily  of  a technical  character,  and  is  not  intended  for  general 
distribution  among  the  public.  It  is  assumed  that  engineers  and 
manufacturers  who  will  have  occasion  to  refer  to  this  publication 
have  at  least  an  elementary  knowledge  of  chemistry. 


Digitized  by  the  Internet  Archive 
in  2017  with  funding  from 

University  of  Illinois  Urbana-Champaign  Alternates 


https://archive.org/details/testingofroadoilOOroma 


INTRODUCTION. 


The  study  of  the  nature  and  character  of  road  oils  has  become 
a subject  of  special  importance  in  the  Middle  West  where  these 
oils  are  being  used  extensively  in  the  surface  treatment  of  earth 
roads. 

It  is  estimated  that  in  Illinois  alone,  approximately  two  hundred 
thousand  dollars  ($200,000)  were  spent  for  road  oils  applied  during 
1915,  and  that  this  amount  has  been  more  than  doubled  in  1916. 

A large  per  cent  of  the  road  oils  used  in  the  past  was  pur- 
chased by  townships  and  often  the  only  requirement  made  has 
been  that  the  product  should  have  a certain  gravity  or  a certain 
per  cent  of  “asphaltum.”  No  temperature  at  which  the  gravity  of 
the  oil  was  to  be  taken  was  given,  and  the  consistency  of  the 
“asphaltum”  or  residue  to  be  obtained  was  not  specified.  The 
absurdity  of  such  specifications  will  be  shown  further,  by  the 
fact  that  road  oils  having  the  same  gravity  at  a given  temperature, 
or  having  the  same  per  cent  of  residue  or  “asphaltum”  of  a given 
consistency,  may  be  of  entirely  different  character. 

It  has  been  a source  of  gratification  to  note,  however,  that  the 
number  of  oils  purchased  in  the  past  year  under  suitable  specifica- 
tions has  increased  considerably  and  that  the  character  of  the  oils 
used  has  been  in  general  much  better  than  in  past  years. 

SOURCE  AND  CHARACTER  OF  ROAD  OILS. 

Road  oils  are  either  crude  petroleum  or  petroleum  products. 
It  should  be  noted,  however,  that  a few  of  the  heavier  oils  consist 
mainly  of  asphalts  which  have  been  fluxed  with  light  oils. 

It  is  not  the  purpose  of  the  writer  to  enter  into  a discussion  of 
the  origin  of  petroleum,  but  in  order  to  understand  the  character 
of  the  various  types  of  road  oils,  it  is  necessary  to  say  a few  words 
concerning  the  source  of  the  petroleums  and  the  petroleum  products 
used  in  Illinois.  With  the  exception  of  a small  amount  of  Mexican 
and  Trinidad  products,  the  petroleums  and  petroleum  products  used 
in  Illinois  are  obtained  almost  entirely  in  the  United  States.  The 
main  oil  fields  are  generally  divided  as  follows : 

(1)  Appalachian  field;  (2)  Ohio-Indiana-Illinois  field;  (.3) 
Mid-Continent  field ; (4)  Gulf  field ; (5)  California  field. 

Petroleum  from  different  parts  of  the  same  field  may  vary  con- 
siderably and  may  show  greater  variations  than  oils  from  different 
fields. 

The  petroleums  high  in  paraffins  are  obtained  in  the  Appala- 
chian, the  Ohio-Indiana-Illinois  and  the  Mid-Continent  fields.  The 
Ohio-Indiana-Illinois  oils  are  somewhat  heavier  than  the  Pennsyl- 
vania oils  (Appalachian  field)  and  contain  much  larger  quantities 


8 


of  sulphur  compounds.  Some  of  the  southern  Illinois  oils  contain 
a fairly  large  per  cent  of  asphaltic  hydrocarbons,  and  for  road  build- 
ing purposes  resemble  closely  the  best  Kansas  and  Oklahoma  oils. 
The  Mid-Continent  field  comprising  Oklahoma  and  Kansas,  pro- 
duces petroleums  which  vary  rather  widely,  but  which  as  a rule 
contain  less  paraffins  and  more  asphaltic  hydrocarbons  than  the 
oils  from  the  Appalachian  and  Ohio-Indiana-Illinois  fields. 

The  petroleums  from  the  Gulf  field,  comprising  Texas  and 
Louisiana,  leave  a fairly  heavy  residue  and  contain  only  a small 
per  cent  of  solid  paraffins.  For  road  purposes  they  may  be  con- 
sidered as  intermediary  products  between  the  paraffin  petroleums 
described  and  the  asphaltic  petroleums  of  California  and  Mexico. 

The  California  field  produces  petroleums  which  consist  mainly 
of  asphaltic  hydrocarbons.  They  leave  heavy  residuums  which 
show  good  binding  qualities  and  which  are  generally  superior  for 
road  purposes  to  all  the  other  petroleum  residuums  of  the  United 
States. 

It  will  be  seen  that  from  the  standpoint  of  road  oils  alone,  the 
five  petroleum  fields  described  produce  three  types  of  oils,  the 
paraffin,  the  semi-asphaltic,  and  the  asphaltic  products  represented 
by  the  Pennsylvania,  Texas  and  California  oils  respectively. 

The  crude  oils  of  each  type  may  vary  widely  in  consistency 
from  light  liquids  which  flow  freely  to  heavy  liquids  so  viscous  that 
they  can  be  pumped  only  with  great  difficulty.  Some  crude  petro- 
leums are  available  which  as  such  are  satisfactory  for  road  pur- 
poses, while  others  may  require  refining  or  fluxing.  A small 
amount  of  refining  rapidly  increases  the  price  of  road  oils  on  account 
of  the  cost  of  handling,  and  it  has  therefore  been  the  tendency 
to  sell  as  road  oils  many  crude  petroleums  which  are  entirely  un- 
satisfactory for  road  building  purposes.  Before  taking  up  the 
methods  of  examining  these  products  it  is  necessary  to  say  a few 
words  in  regard  to  the  chemical  composition  of  road  oils. 

CHEMICAL  COMPOSITION  OF  ROAD  OILS. 

Road  oils  consist  mainly  of  hydrocarbons  with  generally  some 
sulphur  compounds  and  small  amounts  of  nitrogen  and  oxygen  deriva- 
tives of  some  of  the  hydrocarbons.  As  stated  previously,  the  road  oils 
from  the  eastern  field  consist  mainly  of  hydrocarbons  of  the  paraffin 
series  (Cn  H2n+2).  These  hydrocarbons  are  also  found  in  large 
quantities  in  the  Ohio,  Indiana,  Illinois,  Kansas  and  Oklahoma  petro- 
leums, but  the  best  road  oils  from  these  states  contain  also  saturated 
hydrocarbons  of  the  Cn  H2n_2  and  Cn  H2a_4  series  and  also  some 
unsaturated  hydrocarbons.  The  California  road  oils  consist  largely  of 
unstable  polymethylene  hydrocarbons  and  leave  residues  showing  a 
large  per  cent  of  unsaturated  hydrocarbons.  The  Texas  road  oils 
consist  mainly  of  paraffin  and  of  stable  polymethylene  hydrocarbons. 

Hydrocarbons  of  the  olefine  or  ethylene  series  Cn  H2n  and  some 
aromatic  hydrocarbons  are  present  in  most  of  the  road  oils.  The 
naphthenes  or  monocyclic  poly  methylene  hydrocarbons  mainly  of  the 


9 


hexamethylene  series  are  found  in  most  of  the  semi-asphaltic  and 
asphaltic  road  oils. 

As  will  be  seen  from  the  above  outline,  road  oils  are  extremely 
complex  mixtures  of  various  hydrocarbons  belonging  to  a number  of 
different  series.  That  it  would  be  an  impracticable  task  to  isolate  the 
hydrocarbons  in  road  oils  can  be  readily  understood  when  it  is  stated 
that  according  to  Hubbard  (Dust  Preventives  and  Road  Binders),  the 
lowest  member  of  the  paraffin  series  which  might  be  found  in  road 
oils  is  pentane  C5  H12  and  that  the  known  normal  paraffins  run  as  high 
as  C60  H122.  Each  member  of  this  series  has  a number  of  isomers 
and  their  number  increases  rapidly  with  the  increase  of  carbon  atoms, 
hexane,  (C6  H14)  having  six  isomers  while  tridecane  (C13  H28)  has 
802  isomers.  The  number  of  paraffin  hydrocarbons  alone  which  might 
exist  in  road  oils  is  therefore  enormous. 

As  each  series  of  hydrocarbons  which  may  be  present  in  a road 
oil  usually  imparts  some  special  property  to  the  oil,  it  is  necessary  to 
say  a few  words  of  some  of  the  characteristics  of  the  most  important 
series. 

The  paraffins  give  a greasy  appearance  to  road  oils  and  their 
presence  in  large  quantities,  especially  of  the  solid  paraffins,  indicate 
that  the  oil  has  poor  binding  qualities.  The  higher  members  of  the 
paraffin  series  which  are  solid  at  room  temperature  dissolve  readily  in 
the  lower  members  of  the  series  which  are  liquid.  This  fact  is  used 
as  a means  of  separating  from  the  paraffins  and  other  saturated  com- 
pounds the  heavy  unsaturated  hydrocarbons  which  are  insoluble  in 
paraffin  naphtha.  The  lower  members  of  the  paraffin  series  are  readily 
soluble  in  alcohol  and  ether,  but  the  higher  members  which  are  solid 
at  room  temperature  are  much  less  soluble,  and  are  practically  insoluble 
at  low  temperatures.  This  property  of  the  paraffins  has  been  made 
the  basis  of  a method  for  determining  the  solid  paraffins  or  the 
so-called  paraffin  scale.  The  paraffins  are  probably  the  most  stable 
hydrocarbons,  and  are  not  attacked  by  sulphuric  or  nitric  acid. 

The  cylic  hydrocarbons  of  the  naphthene  or  monocyclic  poly- 
methylene series  and  of  the  polycyclic  polymethylene  series  are  not 
attacked  by  sulphuric  acid,  but  are  not  as  stable  as  the  paraffins.  The 
polycyclic  polymethylenes,  a number  of  which  have  probably  very  com- 
plex structures,  are  less  stable  than  the  monocyclic  polymethylenes. 
They  are  found  mainly  in  asphaltic  and  semi -asphaltic  road  oils;  and, 
in  oils  which  show  very  little  paraffin  scale,  they  constitute  probably  a 
large  per  cent  of  the  portion  of  oil  which  is  not  removed  by  concen- 
trated sulphuric  acid. 

The  unsaturated  hydrocarbons  comprising  the  olefines,  the 
camphan  group  of  terpenes  and  a number  of  aromatic  and  straight 
chain  compounds  which  occur  more  or  less  frequently  in  road  oils, 
probably  do  not  all  have  the  same  value  in  road  oils,  but  it  has  been 
noted  that  in  general  the  higher  is  the  per  cent  of  bitumen  removed  by 
sulphuric  acid,  the  better  are  the  binding  qualities  of  various  road 
oils.  Some  of  these  unsaturated  hydrocarbons  appear,  therefore,  to 
give  adhesiveness  to  the  oils  and  to  the  residual  asphalts  obtained  from 


10 


road  oils  showing  large  percentages  of  bitumen  removed  by  sulphuric 
acid. 

METHODS  OF  TESTING. 

In  general,  the  methods  described  in  the  following  pages  are  not 
new,  and  a number  of  them  have  been  used  in  asphalt  testing  for  a 
number  of  years.  Nearly  800  samples  of  road  oils  have  been  examined 
in  the  laboratory  of  the  Illinois  State  Highway  Department  during  the 
past  four  years,  and- some  of  the  methods  have  been  somewhat  modi- 
fied in  order  to  make  them  suitable  for  the  testing  of  road  oils.  Most 
of  the  comments  and  suggestions  which  are  found  in  the  following 
description  of  these  tests  represent  the  results  of  the  experience  of  the 
laboratory  in  the  examination  of  oils,  and  of  observations  of  the 
results  obtained  with  these  oils  in  the  field,  mainly  on  earth  roads. 

SPECIFIC  GRAVITY. 

The  specific  gravity  of  road  oils  is  generally  taken  at  25 °C. 
(77°F.)  as  compared  with  water  at  the  same  temperature.  This  is 
about  the  average  temperature  at  which  road  oils  are  handled.  It  has 
been  found  to  be  more  convenient,  therefore,  to  determine  their  gravity 
at  25°C.  than  at  15.5°C.  (60°F.),  the  temperature  at  which  the 
specific  gravity  of  most  oils  is  generally  taken. 

The  specific  gravity  of  the  thin  fluid  road  oils  is  determined 
usually  by  means  of  either  a hydrometer  or  a Westphal  balance,  but 
it  may  be  determined  also  by  the  pycnometer  method.  Hydrometers 
and  Westphal  balances  are  generally  calibrated  to  give  specific  gravity 
readings  at  15.5°C.  With  such  instruments  the  determination  is  car- 
ried on  at  25 °C.  as  usual  and  a correction  applied  to  the  specific 
gravity  reading.  For  ordinary  practical  work  this  reading  may  be  cor- 
rected to  water  at  25°C.,  considered  as  unity,  by  multiplying  by  1.002 
as  follows : 

Specific  gravity  at  25°C./25°C.  = specific  gravity  at  25°C./15.5°C. 
X 1-002. 

In  practical  field  work  the  gravity  of  road  oils  is  often  expressed 
by  means  of  the  Beaume  scale.  The  specific  gravity  at  25°C.  of  road 
oils  commonly  used  being  in  general  less  than  unity,  their  gravity  in 
degrees  Beaume  may  be  obtained  from  their  specific  gravity  by  means 
of  the  following  tables  or  by  means  of  the  formula: 

140 

Degrees  Beaume  = 130  at  15.5°C. 

specific  gravity 

COMPARISON  OF  DEGREES  BEAUME  AND  SPECIFIC 

GRAVITY. 

(Liquids  lighter  than  water.) 


°B. 

Sp.  Gr. 

°B. 

Sp.  Gr. 

°B. 

Sp.  Gr. 

10 

1.0000 

22 

.9210 

34 

.8536 

11 

.9929 

23 

.9150 

35 

.8484 

12 

.9859 

24 

.9090 

36 

.8433 

13 

.9790 

25 

.9032 

37 

.8383 

11 


°B. 

Sp.  Gr. 

°B 

Sp.  Gr. 

°B. 

Sp.  Gr. 

14 

.9722 

26 

.8974 

38 

.8333 

15 

.9655 

27 

.8917 

39 

.8284 

16 

.9589 

28 

.8860 

40 

.8235 

17 

.9523 

29 

.8805 

41 

.8187 

18 

.9459 

30 

.8750 

42 

.8139 

19 

.9395 

31 

.8695 

43 

.8092 

20 

.9333 

32 

.8641 

44 

.8045 

21 

.9271 

33 

.8588 

Either 

the  hydrometer 

or 

the  Westphal  balance  may  be  used  for 

making  a rapid  determination  of  the  gravity  of  thin  fluid  products,  the 
Westphal  balance  being  more  satisfactory  for  accurate  work.  Neither 
apparatus  is  suitable,  however,  for  the  determination  of  the  gravity 
of  viscous  oils.  Figure  1 shows  a type  of  Westphal  balance  satisfac- 
tory for  road  oil  testing,  and  Figure  2 shows  a hydrometer  and 
hydrometer  jar.  When  using  hydrometers  with  road  oils,  care  should 
be  taken  to  let  the  instrument  sink  slowly  in  the  oil  until  it  has  come 
to  rest.  The  reading  obtained  should  be  checked  by  raising  the 
hydrometer  a few  degrees  and  letting  it  sink  again.  The  hydrometer 
should  not  be  pushed  below  the  point  at  which  it  comes  to  rest  until 
the  readings  have  been  completed.  To  judge  if  the  oil  is  too  viscous 
for  a satisfactory  determination  of  the  gravity,  the  hydrometer  should 
be  sunk  in  the  oil  3 or  4 degrees  below  its  resting  point.  If  it  should 
not  begin  to  rise  at  once,  the  oil  is  too  viscous  for  the  hydrometer 
method,  and  the  pycnometer  must  be  used. 

The  Hubbard  type  of  pycnometer  is  used  for  the  determination 
of  the  gravity  of  almost  all  heavy  viscous  road  oils,  and  is  suitable 
also  for  the  lighter  oils.  This  type  of  pycnometer  is  shown  in 
Figure  3 and  consists  of  a straight  walled  glass  tube,.  70  milli- 
meters in  length  and  22  millimeters  in  diameter,  with  a heavy 
ground  glass  stopper  bored  with  a hole  1.6  millimeters  in  diameter. 
When  stoppered  the  pycnometer  has  a Capacity  of  about  24  cubic 
centimeters.  With  fluid  oils  the  specific  gravity  determination 
using  this  type  of  pyncometer  is  similar  to  the  determination  with 
the  ordinary  pycnometers.  The  weight  of  the  oil  which  will  fill 
the  pycnometer  at  25°  C.  is  divided  by  the  weight  of  the  same 
volume  of  water  afi  the  same  temperature. 

With  the  viscous  road  oils  the  following  method  of  determin- 
ing their  specific  gravity  is  used,  all  weighings  being  made  with 
the  stopper  in  place  on  the  pycnometer.  The  weights  of  the  empty 
pycnometer  and  of  the  pycnometer  filled  with  water  at  25°  C.  are 
determined  as  usual  and  called  “a”  and  “b”  respectively.  The 
road  oil  is  heated  until  it  pours  readily  and  the  pycnometer  is  filled 
to  about  three-fourths  of  its  volume,  taking  care  that  no  oil  comes 
in  contact  with  the  stopper.  After  cooling,  the  pycnometer  and 
contents  are  weighed  and  the  weight  called  “c.”  Enough  dis- 
tilled water  is  then  poured  on  top  of  the  oil  to  fill  the  pycnometer, 
which  is  then  immersed  for  at  least  20  minutes  in  a beaker  of  dis- 
tilled water  at  25°  C.  Although  their  gravity  is  less  than  that  of 


12 


water,  the  heavy  viscous  oils  will  give  no  trouble  in  this  operation. 
Less  viscous  oils  show,  however,  a lower  gravity  and  less  adhesive- 
ness, and  will  tend  to  float  on  the  water.  The  specific  gravity  of 
these  oils  may  often,  however,  be  determined  by  this  method  by 
taking  care  to  add  the  water  slowly  around  the  sides  of  the  pycno- 


m 


/yy  t/ydron?  e ter  Method 


F/y.J-Pyenom  efer 

(/tub bard  Type) 


meter.  Should  this  fail  to  keep  the  oil  from  floating,  some  other 
method  of  determining  its  gravity  must  be  adopted. 

The  pycnometer  with  the  oil  and  water  at  25°  C.  are  weighed 
and  this  weight  is  called  “d.”  All  the  values  necessary  to  calculate 


the  specific  gravity  are  now  available,  and  the  following  formula 
which  will  be  readily  understood  is  obtained : 

c — a 

Specific  gravity  at  25°C./25°C.  = . 

(b  — a)  — (d  — c) 

“a”  and  “b”  are  constants  and  after  being  determined  once  they 
need  to  be  checked  only  from  time  to  time. 

The  specific  gravity  at  25°  C.^(77°  F.)  of  light  fluid  road  oils  of 
a paraffin  nature  for  cold  application  vary  from  about  0.890  to  0.930, 
while  the  specific  gravity  of  the  corresponding  asphaltic  oils  is 
slightly  higher  from  about  0.910  to  0.950.  The  heavy  viscous 
asphaltic  oils  which  are  applied  hot  have  a specific  gravity  at  25°  C. 
(77°  F.)  varying  from  about  0.950  to  unity. 

As  a rule  the  determination  of  the  specific  gravity  alone  is  of 
little  value  in  the  examination  of  road  oils,  but  if  taken  in  connec- 
tion with  other  tests,  it  is  of  value  to  check  the  nature  and  source 
of  these  oils. 

It  should  be  noted  in  connection  with  this  test  that  the  volume 
of  road  oils  increases  when  their  temperature  is  raised,  and  that 
their  gravity  shows  a corresponding  decrease.  A specification 
requiring  a given  gravity  for  an  oil  without  stating  the  temperature 
at  which  the  gravity  is  to  be  determined  is,  therefore,  worthless. 

The  coefficient  of  expansion  of  road  oils,  that  is  the  ratio 
between  the  increase  in  volume  of  the  oils  when  their  temperature 
is  raised  one  degree  and  the  original  volume  of  these  oils,  varies 
somewhat  with  the  nature  and  character  of  the  oils  and  the  tem- 
perature at  which  this  coefficient  of  expansion  is  measured.  For 
most  practical  purposes  the  coefficient  of  expansion  of  road  oils, 
when  their  volume  at  25°  C.  (77°  F.)  is  taken  as  unity,  may  be 
assumed  to  be  0.0007  per  degree  centigrade,  and  0.0004  per  degree 
Fahrenheit.  Thus  if  V is  the  original  volume  of  the  oil,  its  volume  V1 
when  the  temperature  has  been  raised  20  degrees  centigrade  will  be  V 
(1  -f~  (20  X 0.0007)  or  V (1  + 0.014)  or  V X 1.014.  This  should  be 
taken  into  consideration  in  the  measurements  of  road  oils  by  volume. 
An  oil  measured  hot  at  a temperature  of  177° F.  would  show  a decrease 
per  unit  of  volume  when  cooled  to  a temperature  of  77°F.  of 
(177 — 77)  X 0.0004  = 0.04  or  in  other  words,  a decrease  of  4 per 
cent  by  volume. 

SPECIFIC  VISCOSITY. 

The  Engler  viscosimeter  is  generally  used  for  this  determination. 
Other  types  of  viscosimeters  will  undoubtedly  give  satisfactory  results, 
but  on  account  of  the  ease  with  which  it  can  be  cleaned,  the  Engler 
type  has  been  generally  adopted. 

It  is  shown  in  Figure  4,  and  consists  of  a brass  vessel  “a”  with 
gold  plated  interior  for  holding  the  road  oil.  This  vessel  has  a cover 
“b”  and  is  fitted  with  an  outflow  tube  “c,”  exactly  20  mm.  in  length 
with  a diameter  of  2.9  mm.  at  the  top  and  2.8  mm.  at  the  bottom.  The 
tube  can  be  closed  with  the  wooden  plug  “ d 


14 


Three  metallic  projections  are  placed  in  “a”  at  equal  distances 
from  the  bottom  and  serve  to  measure  the  charge  of  240  cubic  centi- 
meters. The  thermometer  “e”  shows  the  temperature  of  the  road  oil, 
while  the  thermometer  “f”  gives  the  temperature  of  the  heating  bath. 
The  thermometer  “e”  is  made  especially  for  this  apparatus  and  is 


graduated  either  to  50°C.,  100°C.,  or  150°C.  The  brass  jacket  “g”  is 
nearly  filled  either  with  water  or  a high  boiling  oil  acting  as  a heating 
bath.  The  apparatus  is  supported  on  a tripod  “h”  to  which  is  attached 
a ringburner  “i”  for  heating  the  bath.  The  oil  is  received  in  a 50  cc. 


15 


cylinder  “j”  which  has  been  found  most  satisfactory  for  all  practical 
work. 

Special  care  should  be  taken  to  keep  the  vessel  “a”  and  the  outflow 
tube  “c”  perfectly  clean.  It  is  also  sometimes  necessary  to  remove 
impurities  from  the  road  oil  by  straining  it  through  a cheesecloth 
before  performing  the  viscosity  test. 

The  viscosity  determinations  are  made  at  various  temperatures, 
25°C,  50°C.,  and  100°C.  being  generally  adopted.  As  all  viscosity 
determinations  should  be  compared  with  water  at  25 °C.  the  apparatus 
should  first  be  calibrated  with  water,  after  it  has  been  thoroughly 
cleaned.  With  the  required  charge  of  240  cc.  an  Engler  viscosimeter 
will  deliver  the  first  50  cc.  in  about  11  seconds  and  the  first  100  cc.  in 
about  23  seconds.  The  time  of  flow  is  measured  with  a stop  watch 
which  is  started  at  the  same  time  that  the  plug  “d”  is  removed  and  is 
stopped  when  the  oil  has  reached  the  required  mark  on  the  receiving 
cylinder.  With  proper  care  of  the  apparatus,  the  time  of  flow  of  water 
at  25 °C.  should  remain  a constant  and  will  require  checking  only  at 
long  intervals. 

It  is  essential  that  all  the  oil  of  the  charge  be  at  the  required 
temperature  when  its  viscosity  is  determined.  The  fluid  oils  should 
remain  at  the  temperature  chosen  for  a least  3 minutes,  and  the  heavy 
viscous  road  oils  for  at  least  5 minutes  just  previous  to  the  time  of 
measuring  their  viscosity.  With  a little  experience  the  temperature 
of  the  heating  bath  may  be  regulated  so  as  to  keep  the  temperature  of 
the  oil  in  the  inner  vessel  practically  constant. 

The  specific  viscosity  of  the  oil  compared  with  water  at  25 °C.  is 
obtained  by  dividing  the  time  of  flow  of  a certain  number  of  cubic 
centimeters  of  the  oil  by  the  time  of  flow  of  the  same  number  of  cubic 
centimeters  of  water  at  25 °C.  Thus  : 

~ ~ Time  of  flow  of  50  cc.  of  oil  at  X°C. 

Specific  viscosity 

at  X C./25  C.  Time  of  flow  of  50  cc.  of  water  at  25°C. 

The  determination  of  the  specific  viscosity  of  a road  oil  is  of  great 
value  in  determining  whether  the  oil  may  or  may  not  be  applied  cold, 
and  if  heating  is  required,  the  temperature  at  which  it  should  be 
applied.  It  permits  also  to  judge  if  an  oil  is  of  the  proper  consistency 
for  certain  types  of  road  construction.  The  viscosity  of  oils  which 
are  to  be  applied  cold  is  generally  taken  at  50°C.  The  viscosity  of 
oils  which  are  to  be  applied  cold  from  gravity  distributors  is  often 
taken  also  at  a lower  temperature,  preferably  25°C.  The  viscosity  of 
road  oils  which  will  be  heated  with  steam  coils,  should  be  taken  at 
50°C.  and  100°C,  while  the  viscosity  of  the  heavy  asphaltic  oils, 
which  will  require  heating  to  temperatures  above  steam  heat  before 
application,  should  be  taken  at  temperatures  of  100°C.  and  possibly 
150°C.  An  oil  with  a specific  viscosity  of  more  than  60  at  25°C.  and 
more  than  15  at  50°C.  can  not  always  be  applied  cold  from  gravity 
distributors.  Pressure  distributors  will  not  always  handle  properly 
cold  oils  having  a specific  viscosity  at  50°C.  of  more  than  20,  although 
in  hot  summer  weather  an  oil  with  a specific  viscosity  as  high  at  70  at 


16 


50°C..  has  been  applied  without  heating.  It  is  difficult,  under  certain 
conditions,  to  heat  with  steam  to  a satisfactory  fluidity  an  oil  having 
a specific  viscosity  at  100°C.  of  more  than  15,  but  on  hot  summer  days 
it  is  possible  to  heat  with  steam,  to  a satisfactory  fluidity,  an  oil  show- 
ing a specific  viscosity  at  100°C.  as  high  as  30. 

It  should  be  noted  that  it  has  been  the  tendency  within  the  past 
years  to  heat  road  oils  which  might  have  been  applied  cold.  The  appli- 
cation of  the  oil  after  heating  instead  of  cold,  appears  to  give  some- 
what better  results  on  earth  roads,  as  the  oil  being  somewhat  more 
fluid  will  be  distributed  somewhat  more  uniformly  over  the  road 
surface,  and  on  cold  days  the  danger  of  having  the  oil  “cake”  on  the 
surface  of  the  road  is  eliminated. 

VOLATILIZATION  LOSS. 

The  purpose  of  this  test  is  to  determine  the  per  cent  of  the  oil 
which  will  volatilize  when  a given  quantity  of  the  oil  in  a standard  size 
container  is  maintained  at  a certain  temperature  for  a given  number  of 
hours. 

The  volatilization  test  which  has  been  considered  as  a standard 
test  for  asphalts  and  road  oils  in  the  past  years  (See  1915  Year  Book 
of  the  American  .Society  for  Testing  Materials)  is  to  heat  20  grams  of 
the  material  contained  in  a seamless  tin  box  2 y2  inches  in  diameter 
and  24  inches  deep  (about  6 cm.  in  diameter  and  2 cm.  deep)  for  5 
hours  at  a temperature  of  163°C.  (325°F.)  in  a New  York  Testing 
Laboratory  oven.  This  type  of  oven  is  shown  in  Figure  5,  and  has 
been  most  commonly  used,  although  other  types  of  ovens  which  can 
be  regulated  to  give  uniform  temperature  will  undoubtedly  give  satis- 
factory results. 

The  New  York  Testing  Laboratory  Oven  is  made  either  of  iron 
or  copper,  covered  on  the  outside  with  asbestos.  It  is  constructed  in 
such  a way  that  it  provides  a uniform  circulation  of  air.  It  is  heated 
with  gas  by  means  of  the  ring  burner  “a,”  and  the  gas  supply  is 
regulated  by  means  of  the  mercury  thermostat  “b.”  With  a fairly 
uniform  gas  presssure  this  attachment  will  permit  to  regulate  the  heat 
in  the  oven  within  one  or  two  degrees  of  the  temperature  desired. 

When  a road  oil  is  heated  the  two  thermometers  “c”  and  “d”  are 
used.  The  bulb  of  the  thermometer  “c”  is  immersed  in  a non-volatile 
oil  and  shows  the  temperature  of  the  road  oil  during  the  volatilization 
test.  The  thermometer  “d”  is  kept  in  air  at  about  the  'same  level  as 
“c”  and  is  used  to  give  warning  of  any  sudden  change  in  the  temper- 
ature of  the  air  in  the  oven  due  to  possible  irregularities  in  the  gas. 
•supply,  “e”  is  the  top  of  the  oven  and  shows  the  openings  which  per- 
mit a satisfactory  circulation  of  air. 

The  oven  should  be  brought  to  the  required  temperature  before  the 
cup  containing  the  oil  to  be  tested  is  inserted.  When  the  oil  has  been 
heated  for  the  required  length  of  time,  it  should  be  removed  to  a 
desiccator  and  allowed  to  cool  before  weighing.  The  original  weight 
of  the  oil  taken  should  be  within  0.2  gms.  of  20  gms,  and  the  weighings 
should  be  accurate  to  the  third  decimal  place. 


17 


Because  of  the  fact  that  the  residues  obtained  after  submitting 
20  grams  of  the  oil  to  the  volatilization  test  are  often  too  small  to  per- 
mit their  examination  in  a satisfactory  manner,  many  of  the  labora- 
tories have  adopted  the  use  of  a 50-gram  sample  for  the  volatization 
test.  The  container  for  the  50-gram  sample  should  be  a tin  seamless 


box  similar  to  a 3-ounce  gill  style  ointment  box,  deep  pattern.  It 
should  have  a flat  bottom  and  vertical  sides  and  should  be  5)4  cm.  in 
diameter  and  3 ]/2  cm.  deep  (approximately  2-3/16  inches  in  diameter 
and  1 y%  inches  in  depth). 


The  American  Society  for  Testing  Materials  recommends  in 
their  1916  revised  “Standard  Tests  for  Loss  on  Heating  of  Oil  and 
Asphaltic  Compounds”  (A.  S.  T.  M.  Standards,  1916)  that  in  addi- 
tion to  the  adoption  of  a 50-gram  sample  a special  type  of  oven  be 
used.  This  oven  may  be  either  of  circular  or  retangular  form,  and 
the  source  of  heat  may  be  either  gas  or  electricity.  The  most  impor- 
tant feature  of  this  type  of  oven  is  that  the  shelf  which  carries  the 
samples  is  suspended  by  a vertical  shaft  midway  in  the  oven,  and  is 
revolved  by  means  of  a motor  at  a speed  of  5 to  6 revolutions  per 
minute.  This  shelf  which  is  perforated,  has  a diameter  of  24.8  cm. 
(9^4  inches),  and  the  samples  all  rest  in  the  same  relative  position  in 
a circular  row. 

It  should  be  noted  in  connection  with  the  volatilization  of  a num- 
ber of  samples  of  oils  at  one  time  in  the  same  oven,  that  this  procedure 
is  not  to  be  recommended  when  the  samples  represent  materials  of 
different -character.  It  has  been  noted  repeatedly  that  when  a heavy 
asphalt  consisting  exclusively  of  high  boiling  hydrocarbons  is  heated 
in  an  oven  containing  an  oil  rich  in  low  boiling  hydrocarbons,  the 
asphalt  having  the  high  flash  point  will  show  less  loss  than  when  it  is 
heated  alone  in  the  oven,  and  in  some  cases  will  show  a slight  increase 
in  weight  due  probably  to  the  absorption  of  some  of  the  volatile  pro- 
ducts of  the  oil  having  the  low  flash  point.  It  is,  therefore,  probable 
that  when  a number  of  road  oils  which  have  different  flash  points  are 
heated  together  in  an  oven,  the  volatilization  losses  will  not  be  the 
same  as  those  obtained  when  each  oil  is  heated  alone,  and  in  some 
cases  an  appreciable  error  may  be  noted.  This  is  especially  true  when 
ovens  of  the  New  York  Testing  Laboratory  type  are  used,  but  prob- 
ably to  a much  lesser  degree  when  ovens  with  a revolving  shaft  of  the 
Frease  Electric  type  are  used. 

As  the  volatilization  loss  depends  to  some  extent  of  the  ratio  of 
the  exposed  surface  of  oil  to  the  volume  of  the  oil  and  also  of  the 
shape,  size  and  depth  of  the  container,  it  is  essential  that  the  tin  boxes 
which  have  been  described  above  and  which  have  been  generally 
adopted,  be  used  in  all  cases  if  comparative  results  are  to  be  obtained. 
It  should  be  noted  that  the  20  gram  and  50  gram  samples  may  show 
volatilization  losses  which  vary  materially. 

The  volatilization  test  is  sometimes  undertaken  at  various  temper- 
atures other  than  163°C.,  generally  at  105°C.  or  110°C.,  and  at 
205°C.  or  210°C.,  and  the  length  of  heating  is  sometimes  varied  from 
1 to  7 hours.  Specifications  requiring  a volatilization  test  should, 
therefore,  contain  statements  as  to  the  temperature  at  which  the  oil  is 
to  be  heated,  the  length  of  time  of  volatilization,  the  type  of  oven  used, 
and  the  quantity  of  oil  taken  for  the  test. 

This  test  is  mainly  of  value  in  determining  the  “setting”  or  hard- 
ening properties  of  the  heavier  oils.  An  examination  of  the  residue 
obtained  by  this  test  will  sometimes  give  information  also  as  to  the 
nature  of  the  oil.  The  volatilization  test  is  of  very  little  value,  how- 
ever, when  used  in  the  examination  of  many  of  the  light  oils  which  are 
used  on  earth  roads. 


19 


SOLID  RESIDUE. 

The  purpose  of  this  test  is  to  determine  the  per  cent  of  solid 
residue  or  so-called  “asphaltum”  which  may  be  obtained  from  an  oil. 
A‘  given  quantity  of  the  road  oil,  generally  20  grams  or  50  grams  is 
kept  at  temperatures  only  high  enough  to  produce  volatilization  of  the 


lower  boiling  compounds,  until  the  residue  will  become  solid  on  cooling 
and  show  the  consistency  desired.  The  apparatus  used  to  measure  the 
consistency  of  this  residue  is  the  same  as  the  one  used  to  determine 
the  consistency  of  asphalts.  A Dow  penetration  machine  is  generally 


20 


used,  but  a New  York  Testing  Laboratory  penetrometer,  or  a similar 
type  of  machine  will  give  satisfactory  results. 

All  these  machines  measure  the  distance  which  a standard  No.  2 
cambric  needle  (or  a steel  needle  having  a diameter  of  0.040  inch  and 
tapered  *4  inch  to  a sharp  point)  will  penetrate,  under  a certain  weight 
and  during  a given  length  of  time,  a bituminous  material  maintained  at 
a given  temperature.  The  Dow  penetration  machine  (Figure  6)  con- 
sists of  a No.  2 cambric  needle  “a”  inserted  in  a brass  rod  fitting  in 
the  aluminum  rod  “b.”  The  aluminum  rod  is  a part  of  an  aluminum 
frame  work  “c”  weighing  with  the  brass  rod  and  needle  exactly  50 
grams.  It  is  held  at  “d”  by  means  of  a clamp  which  may  be  held  open 
by  means  of  a button.  Additional  weights  of  50  or  150  grams  are 
added  at  “e”  when  the  penetration  is  taken  under  weights  of  100  or 
200  grams.  The  penetration  is  measured  by  means  of  the  rack  “f” 
and  dial  “g.”  The  rack  is  connected  with  a pinion  to  which  is  attached 
the  hand  of  the  dial,  and  penetration  may  be  measured  by  this  arrange- 
ment to  an  accuracy  of  0.1  mm.  The  tin  box  “h”  containing  the 
bituminous  material  is  kept  in  water  at  the  desired  temperature  and 
when  tested  is  placed  on  the  shelf  “i.”  The  time  of  penetration  is 
generally  indicated  by  a metronome,  although  various  electrical  attach- 
ments have  been  devised  for  the  purpose  of  regulating  accurately  the 
time  of  penetration. 

Road  oils  are  generally  heated  until  a residue  is  obtained  which 
has  a penetration  in  5 seconds  at  25°C.  under  a weight  of  100  grams 
of  10  mm.  Road  oils  may  be  heated,  however,  until  softer  or  harder 
residues  are  obtained,  and  the  rather  indefinite  term  “asphaltum”  is 
commonly  given  to  all  of  these  residues.  The  chemical  composition  of 
these  residues  may  vary  widely,  the  paraffin  road  oils  leaving  a greasy 
residue  rich  in  solid  paraffins,  while  some  of  the  best  road  oils  leave  an 
adhesive  residue  consisting  mainly  of  asphaltic  hydrocarbons.  It  will 
be  readily  understood,  therefore,  that  a guarantee,  such  as  some  oil 
companies  give,  of  furnishing  an  oil  with  a certain  per  cent  of  asphal- 
turn  has  no  definite  meaning  and  is  worthless.  Furthermore  the  heating 
of  road  oils  at  temperatures  above  200°C.,  during  the  evaporation 
tends  to  produce  “cracking,”  that  is  the  decomposition  of  some  of  the 
hydrocarbons  and  the  formation  of  new  compounds.  Thus  a paraffin 
might  decompose  into  a paraffin  and  an  olefine  as  follows : 

Cn  (-heat 
paraffin 

Thorpe  and  Young  state  (Ber.  des  Deutch  Chem.  Gesellsch.,  1872, 
p.  536)  that  the  products  obtained  in  cracking  paraffin  petroleums  are 
mixtures  of  several  paraffins  and  olefines.  As  it  is  practically  impos- 
sible to  obtain  a residue  of  suitable  consistency  from  many  oils, 
especially  those  rich  in  paraffins  of  high  boiling  point,  within  a reason- 
able length  of  time  without  heating  them  at  a temperature  above 
200 °C.,  it  is  probable  that  some  “cracking”  often  takes  place  in  this 
test.  Furthermore  an  increase  in  the  rate  of  evaporation  corresponds 
to  a decrease  in  the  amount  of  residue  of  a given  consistency  which  is 


C (n_a)  H2(n_a)+2  + Ca  Hs 


paraffin 


olefine 


21 


obtained,  due  to  the  fact  that  when  the  rate  of  evaporation  is  rather 
high  some  high-boiling  hydrocarbons  are  driven  off  which  remain  in 
the  residue  when  the  rate  of  evaporation  is  very  slow.  The  per  cent 
of  residue  of  a given  consistency  which  is  obtained  from  an  oil  may, 
therefore,  vary  materially.  It  is  difficult  also  to  judge  if  a residue  has 
the  proper  consistency.  A few  minutes  of  heating  may  often  change  a 
residue  from  a product  which  is  too  soft  to  a product  which  is  too 
hard,  and  it  has  been  the  experience  of  the  laboratory  of  the  State 
Highway  Department  that  it  is  often  necessary  to  heat  two  or  three 
samples  of  the  same  oil  before  a residue  of  the  proper  penetration  can 
be  secured. 

The  determination  of  the  per  cent  of  solid  residue  in  road  oils  is 
of  value  in  the  examination  of  new  products,  but  it  should  be  remem- 
bered that  this  test  is  inaccurate  and  often  misleading  as  to  the  quality 
of  an  oil.  It  should  not,  therefore,  be  considered  a standard  test,  and 
specifications  for  the  purchase  of  road  oils  should  never  be  based  solely 
on  a given  per  cent  of  solid  residue  or  “asphaltum.”  It  is,  however, 
the  only  test  of  which  many  township  highway  commissioners  have 
any  knowledge,  mainly  because  of  the  practice  of  oil  manufacturers  of 
selling  oils  with  a guarantee  of  a given  asphaltum  content.  For  this 
reason  a test  for  asphaltum  has  been  retained  in  some  of  the  specifica- 
tions for  road  oils  used  on  earth  roads,  although  it  would  be  generally 
better  practice  to  eliminate  this  test  from  these  specifications  and  to 
require  only  tests  for  gravity,  viscosity,  bitumen  insoluble  in  naphtha, 
etc. 

It  is  to  be  noted  that  the  word  “asphaltum”  as  used  in  connection 
with  road  oils  is  generally  misunderstood  by  the  public.  A 40% 
asphaltum  oil  is  generally  taken  to  mean  that  the  oil  contains  40%  of 
a definite  material  called  “asphaltum.”  It  is  a very  difficult  matter  to 
make  the  average  township  commissioner  understand  that  the  so-called 
“asphaltum’.’  in  an  oil  is  not  a definite  substance  and  that  the  pro- 
portion of  residue  or  asphaltum  obtained  from  an  oil  does  not  neces- 
sarily indicate  the  quality  of  this  oil. 

FLASH  AND  BURNING  POINTS. 

The  purpose  of  these  tests  is  mainly  to  determine  the  highest 
temperature  at  which  an  oil  may  be  heated,  without  danger  of  burning. 
They  serve  also  to  indicate  the  presence  or  absence  of  the  low-boiling 
oils. 

The  tests  may  be  performed  either  in  one  of  the  various  types  of 
closed  testers  or  by  the  open  cup  method.  The  closed  testers  give 
more  accurate  results,  but  for  practical  work  with  road  oils  some  form 
of  open  cup  oil  tester  is  generally  used.  A convenient  form  of  open 
cup  flash  and  burning  point  apparatus  is  shown  in  Figure  7.  The  cup 
“a”  having  a capacity  of  about  100  cc.,  contains  the  oil  to  be  tested, 
while  the  other  vessel  “b”  acts  as  an  air  jacket  heated  by  means  of  a 
spirit  lamp  or  a gas  burner  “c.”  The  thermometer  “d”  is  placed  so 
that  the  entire  bulb  is  immersed  in  the  oil,  but  that  it  does  not  touch 
the  bottom  or  sides  of  the  cup.  In  the  determination  of  the  flash  point 


22 


the  oil  is  heated  so  that  its  temperature  will  be  raised  at  the  rate  of 
5°C.,  per  minute.  A test  flame  is  brought  from  time  to  time  almost  in 
contact  with  the  surface  of  the  oil.  The  most  suitable  test  flame  is  a 


jet  of  gas  from  a piece  of  glass  tubing  drawn  to  a point  with  an  open- 
ing about  1 mm.  in  diameter,  the  flow  of  the  gas  being  regulated  so 
as  to  give  a flame  between  5 and  10  mm.  in  length.  The  temperature 
at  which  the  test  flame  will  produce  the  first  distinct  flash  over  the 
entire  surface  of  the  oil  is  taken  as  the  flash  point  of  the  oil.  If  the 


23 


temperature  of  the  oil  is  raised  further  until  the  oil  will  ignite  and  burn 
when  tested  in  the  manner  described  above,  the  burning  point  of  the 
oil  is  obtained.  The  metal  cover  “e”  is  used  to  extinguish  the  flame. 

It  should  be  remembered  that  the  closed  types  of  oil  tester  give 
lower  results  in  the  determination  of  the  flash  and  burning  points 
than  the  open  cup  testers.  As  stated  previously  the  open  cup  method 
is  accurate  enough  for  most  practical  work,  and  it  is  probable  that 
the  conditions  under  which  the  flash  and  burning  point  determinations 
are  performed  in  the  open  cup  tester  are  very  similar  to  the  working 
conditions  in  the  field. 

The  determination  of  flash  and  burning  points  should  be  made  on 
all  road  oils  which  will  require  heating  before  application.  These 
tests  should  be  performed  also  on  light  oils  which  it  is  intended  to 
apply  cold,  but  which  are  likely  to  contain  some  hydrocarbons  volatile 
at  ordinary  temperature,  and  might  easily  become  accidentally  ignited. 

TOTAL  BITUMEN. 

The  test  consists  in  determining  the  per  cent  of  organic  matter  in 
the  oil  which  is  soluble  in  chemically  pure  carbon  disulphide  at  room 
temperature.  The  amount  of  oil  taken  for  the  determination  will  vary 
with  the  per  cent  of  impurities,  but  with  most  road  oils  about  10  grams 
may  be  used.  The  oil  is  weighed  in  a 150  cc.  Erlenmeyer  flask  and 
50  cc.  of  carbon  disulphide  are  added.  The  contents  of  the  flask  are 
now  agitated  and  given  a whirling  motion  until  no  more  oil  adheres 
to  the  bottom  or  sides  of  the  flask.  After  letting  the  corked  flask 
stand  about  10  minutes,  its  contents  are  filtered  through  a Gooch 
crucible  which  contains  a mat  of  coarse  asbestos  fiber  and  which  has 
been  ignited  and  weighed.  The  usual  filtering  arrangement  is  shown 
in  Figure  8.  The  Gooch  crucible  “a”  fits  tightly  in  the  rubber  tubing 
“b”  which  makes  also  an  air-tight  connection  with  the  funnel  “c.”  The 
stem  of  the  funnel  is  fitted  to  the  filtering  flask  “e”  by  means  of  the 
one  hole  rubber  stopper  “d.”  At  “f”  is  attached  a section  of  pressure 
tubing  which  can  be  connected  to  a suction  pump  when  desired. 

With  most  road  oils  the  carbon  disulphide  solution  can  be  filtered 
without  difficulty  and  the  suction  is  applied  only  to  remove  the  greater 
part  of  the  carbon  disulphide  remaining  in  the  mat,  after  the  contents 
of  the  Erlenmeyer  flask  have  been  transferred  to  the  Gooch  crucible 
and  the  flask  and  crucible  washed  several  times  with  fresh  carbon 
disulphide.  Any  material  which  tends  to  adhere  to  the  bottom  or  sides 
of  the  Erlenmeyer  flask  should  be  removed  to  the  Gooch  crucible  either 
by  means  of  a policeman  or  by  washing  with  carbon  disulphide.  After 
the  filtration  is  completed  the  crucible  is  dried  at  110°C.,  and  weighed, 
and  the  quantity  of  material  insoluble  in  carbon  disulphide  is  calcu- 
lated. The  crucible  is  then  ignited,  and  the  loss  on  ignition  is  taken  as 
the  weight  of  organic  matter  insoluble  in  carbon  disulphide,  and  its 
per  cent  of  the  oil  calculated.  As  some  of  the  inorganic  material  in 
the  oil  is  often  carried  through  the  mat  by  the  carbon  disulphide  solu- 
tion, the  per  cent  of  inorganic  material  in  the  oil  is  not  determined  from 
the  residue  remaining  on  the  Gooch  crucible,  but  is  obtained  from  a 
separate  sample.  It  may  be  determined  directly  by  igniting  1 gram  of 


24 


the  oil  in  a platinum  crucible.  When  a fixed  carbon  determination  is 
performed,  the  per  cent  of  mineral  matter  is  calculated  from  the 
amount  of  ash  obtained.  When  the  amount  of  carbonates  in  the  ash 
is  large,  the  percentage  of  mineral  matter  is  obtained  accurately  by 


moistening  the  ash  with  a few  drops  of  a solution  of  ammonium  car- 
bonate, drying  and  igniting  again  at  a low  heat.  The  crucible  is  then 
cooled  in  a desiccator  and  weighed.  One  hundred  minus  the  percent- 
ages of  organic  matter  insoluble  in  carbon  disulphide  and  of  mineral 


25 


matter  is  taken  as  the  per  cent  of  total  bitumen.  The  mineral  matter 
and  insoluble  organic  matter  are  generally  reported  separately. 

Most  of  the  road  oils  show  very  small  percentages  of  impurities, 
but  as  the  results  of  a number  of  the  tests  are  calculated  in  per  cent 
of  the  total  bitumen,  the  percentages  of  mineral  matter  and  of  organic 
matter  insoluble  in  carbon  disulphide  are  determined  in  all  road  oils. 

BITUMEN  INSOLUBLE  IN-  PARAFFIN  NAPHTHA. 

The  purpose  of  this  test  is  to  separate  from  the  oils  some  of  the 
heavier  hydrocarbons  of  an  asphaltic  nature.  The  test  is  based  on  the 
fact  that  these  heavy  asphaltic  hydrocarbons,  largely  unsaturated  com- 
pounds do  not  dissolve  readily  in  light  paraffin  naphthas  in  which  the 
remaining  portion  of  the  oil  is  soluble.  These  asphaltic  hydrocarbons 
are  less  soluble  in  the  light  naphthas  than  in  naphthas  from  asphaltic 
petroleums.  Care  should  be  taken,  therefore,  to  secure  a suitable 
naphtha  for  testing  purposes  and  its  nature  and  gravity  should  always 
be  indicated  in  reports  of  tests.  The  solvent  used  for  this  determina- 
tion in  most  laboratories  is  a distillate  from  a paraffin  petroleum  pur- 
chased under  the  name  of  86  degrees  Beaume,  paraffin  naphtha.  It 
distills  between  35°C.,  and  75°C.,  and  has  a specific  gravity  at  15.5°C, 
of  about  0.650. 

The  method  of  determining  the  naphtha  insoluble  bitumen  or 
so-called  “asphaltenes”  is  practically  the  same  as  the  method  used  in 
determining  the  inorganic  matter  insoluble  in  carbon  disulphide,  except 
that  86°B.  paraffin  naphtha  is  used  as  the  solvent  instead  of  carbon 
disulphide.  About  10  grams  of  the  light  paraffin  road  oils  may  be 
taken  for  the  test,  but  only  about  2 grams  of  the  heavy  asphaltic  oils 
should  be  used.  In  order  that  the  very  viscous  road  oils  may  be 
attacked  readily  by  the  naphtha,  it  is  sometimes  advisable  to  heat  the 
oil  slightly  after  it  has  been  weighed  in  the  Erlenmeyer  flask,  and  let 
it  cool  in  a thin  layer  at  the  bottom  and  around  the  lower  half  of  the 
flask.  The  filtration  is  carried  on  in  the  same  manner  as  with  the 
carbon  disulphide  solution.  It  is  not  generally  possible  to  transfer  all 
the  insoluble  material  to  the  crucible,  and  the  Erlenmeyer  flask  is  dried 
with  the  crucible  at  110°C.,  and  weighed.  The  total  weight  of  the 
residues  in  the  flask  and  in  the  crucible  are  calculated  in  per  cent  of 
the  weight  of  oil  taken.  It  is  assumed  that  all  the  material  insoluble 
in  carbon  disulphide  is  also  insoluble  in  naphtha,  and  the  difference 
in  per  cent  between  the  material  insoluble  in  carbon  disulphide  and  in 
a given  grade  of  naphtha  is  the  bitumen  insoluble  in  the  naphtha.  Thus 
if  the  oil  shows  0.5%  insoluble  in  carbon  disulphide  and  12.1%  insol- 
uble in  86°B.  paraffin  naphtha,  the  bitumen  insoluble  in  the  naphtha 
would  be  12.1  — 0.5  or  11.6  per  cent  of  the  oil.  The  bitumen  insoluble 
in-  the  naphtha  is  not  generally  expressed  in  per  cent  of  the  oil,  but  in 
per  cent  of  the  total  bitumen  in  the  oil.  Thus  assuming  that  the  oil  con- 
sidered above  shows  99.4%  of  total  bitumen,  the  bitumen  insoluble  in 

11.6  X 100 


86 °B.  paraffin  naphtha  would  be 
the  total  bitumen. 


99.4 


or  about  11.7  per  cent  of 


26 


The  determination  of  the  per  cent  of  total  bitumen  insoluble  in 
paraffin  naphtha  is  of  much  value  in  determining  the  nature  of  road 
oils.  It  should  be  remembered,  however,  that  the  bitumen  insoluble  in 
naphtha  does  not  represent  any  definite  compound  or  any  definite  series 
of  compounds,  but  merely  indicates  that  the  oil  contains  more  or  less 
heavy  hydrocarbons  of  an  asphaltic  nature.  The  light  paraffin  road 
oils  show  generally  less  than  one  per  cent  of  bitumen  insoluble  in 
86°B.  paraffin  naphtha  while  the  very  viscous  oils  of  an  asphaltic 
nature  may  show  as  high  as  15  to  20%  of  bitumen  insoluble  in  the 
same  grade  of  naphtha. 

FIXED  CARBON. 

This  test  is  based  on  the  fact  that  when  they  are  heated  in  a cov- 
ered platinum  crucible  in  the  full  flame  of  a gas  burner,  asphaltic  oils 
leave  a greater  amount  of  residual  carbon  than  the  corresponding 
paraffin  oils.  This  fixed  carbon  is  due  mainly  to  the  decomposition  of 
the  heavier  asphaltic  hydrocarbons  and  to  a smaller  extent  to  the 
decomposition  of  the  heavy  paraffins.  The  method  of  testing  is  derived 
from  the  method  used  in  coal  analysis,  as  described  in  the  Journal  of 
the  American  Chemical  Society,  1899  Vol.  21,  page  1116.  The  plati- 
num crucible  used  weighs  about  25  gms.  with  the  cover.  For  road  oil 
testing  the  cover  of  the  form  of  crucible  generally  used  is  made  with 
a flange  about  4 mm.  wide,  fitting  tightly  over  the  outside  of  the 
crucible.  A sample  of  the  oil  within  two  milligrams  of  1 gram  is 
weighed  into  the  crucible  and  the  covered  crucible  is  then  heated  for 
seven  minutes  over  the  full  flame  of  a Bunsen  burner  as  shown  in 
Figure  9.  The  crucible  is  held  in  a platinum  triangle  supported  by  a 
tripod  of  suitable  height.  Care  should  be  taken  that  the  burner  gives 
a satisfactory  flame  and  that  the  determination  is  made  in  a place  free 
from  drafts.  With  road  oils  the  outside  of  the  crucible  and  upper  side 
of  the  cover  should  burn  clean  without  difficulty  if  the  test  is  per- 
formed under  proper  conditions.  After  heating  for  the  required  length 
of  time  the  crucible  is  placed  in  a desiccator  to  cool.  It  is  then  weighed, 
the  cover  is  removed  and  the  fixed  carbon  attached  to  the  crucible  and 
cover  is  ignited  until  nothing  but  ash  remains.  If  necessary  the  ash 
is  moistened  with  a few  drops  of  a solution  of  ammonium  carbonate 
as  described  under  total  bitumen.  The  crucible  and  cover  are  cooled 
and  weighed,  and  the  per  cent  of  ash  determined.  The  difference 
between  the  weights  of  the  crucible  with  the  fixed  carbon  and  of  the 
crucible  with  the  ash  is  the  weight  of  the  fixed  carbon.  This  weight  is 
generally  reported  in  per  cent  of  the  weight  of  oil,  exclusive  of  the 
mineral  matter. 

There  has  been  much  discussion  as  to  the  value  of  the  fixed  car- 
bon determination.  It  is  contended  that  as  the  carbon  obtained  in 
this  test  is  not  present  as  such  in  the  oil,  it  can  not  properly  be  called 
fixed  carbon  and  that  the  determination  is  useless.  The  fixed  carbon 
test  for  road  oils  gives  valuable  information,  however,  as  to  their 
nature,  and  to  a certain  extent  corroborates  the  results  obtained  from 
the  determination  of  the  naphtha  insoluble  bitumen.  If  used  with  the 
understanding  that  the  results  obtained  merely  serve  to  indicate  the 


27 


nature  of  the  road  oils,  there  can  be  no  objections  to  this  test  except 
when  it  is  used  with  oils  which  foam  badly  or  which  contain  rather 
large  quantities  of  impurities.  In  order  to  obtain  uniform  results  it 
is  necessary,  however,  to  follow  closely  the  method  of  testing  described 
and  to  work  under  conditions  as  uniform  as  possible. 

The  light  paraffin  road  oils' show  only  a small  per  cent  of  fixed 
carbon,  generally  less  than  two  per  cent,  while  the  corresponding 
asphaltic  oils  show  a higher  per  cent  of  fixed  carbon,  the  very  viscous 
asphaltic  oils  showing  as  high  as  15  per  cent  of  fixed  carbon. 

PARAFFIN  SCALE. 

This  determination  is  based  on  the  property  of  the  solid  paraffins 
of  being  practically  insoluble  in  a mixture  of  equal  parts  of  alcohol 
and  ether  at  low  temperatures.  In  order  that  the  paraffins  may  not  be 
contaminated  with  the  impurities  in  the  oil  and  some  of  the  heavier 
asphaltic  hydrocarbons  which  are  insoluble  in  the  ether  and  alcohol 
mixture,  the  oil  is  generally  distilled  and  the  distillate  taken  for  the 
paraffin  determination.  With  light  paraffin  road  oils,  practically  free 
of  impurities  it  may  not  always  be  necessary  to  perform  the  distilla- 
tion, but  the  following  method  may  be  applied  to  all  cases. 

One  hundred  grams  of  the  oil  are  weighed  in  a 250  cc.  iron  or  glass 
retort  and  distilled  as  rapidly  as  possible  to  dry  coke.  The  distillate 
is  received  in  a weighed  Erlenmeyer  flask,  and  when  the  distillation 
has  been  completed,  the  weight  of  the  total  distillate  is  determined. 
From  2 to  5 grams  of  the  distillate  which  has  been  well  mixed  are 
weighed  accurately  in  a 100  cc.  Erlenmeyer  flask  and  dissolved  in  25 
cc.  of  Squibb  ether.  Twenty-five  cc.  of  absolute  alcohol  are  then 
added  and  the  flask  is  packed  in  a freezing  mixture  of  3 parts  of 
finely  chipped  ice  and  1 part  of  salt,  and  the  oil  mixture  is  maintained 
at  a temperature  of  — 20°C.  for  10  minutes.  It  is  then  filtered 
through  the  apparatus  shown  in  Figure  10.  This  apparatus  consists  of 
a Gooch  filter  tube  “a”  with  a long  stem.  The  filter  tube  contains  a 
layer  of  absorbent  cotton  “b”  tightly  packed  and  a layer  of  asbestos 
wool  “c”  covered  with  an  asbestos  mat.  The  filter  tube  is  surrounded 
by  the  freezing  mixture  in  the  container  “d”  made  from  the  upper 
half  of  an  acid  bottle.  The  tube  “e”  serves  to  remove  bv  means  of 
suction  the  salt  solution  produced  by  the  melting  of  the  freezing 
mixture.  As  far  as  possible  the  filter  tube  should  be  kept  loosely  cov- 
ered and  the  freezing  mixture  container  should  be  wrapped  in  towels, 
or  provided  with  a jacket  of  felt  and  suitable  cover. 

When  the  oil  mixture  and  the  apparatus  of  Figure  10  have  been 
cooled  to  a suitable  temperature,  the  oil  mixture  is  transferred  to  the 
filter  tube  and  filtered  as  quickly  as  possible  bv  means  of  suction.  The 
Erlenmever  flask  and  filter  are  then  washed  twice  with  25  cc.  of  a 
mixture  of  1 part  of  Scmibb  ether  and  1 part  absolute  alcohol,  cooled 
to  a temperature  of  — 20°C.  The  filter  tube  is  then  taken  out  of  the 
anoaratus  and  is  fitted  over  a suction  flask  in  a way  such  that  the  stem 
of  the  filter  tube  will  drain  into  a test  tube  or  sample  tube  of  suitable 
size.  Warm  86°B.  naphtha  is  then  added  to  the  filter  tube  and  when 
the  paraffin  scale  has  dissolved,  suction  is  applied.  The  filter  is 


28 


washed  twice  with  about  25  cc.  of  naphtha,  and  the  test  tube,  or 
weighing  tube,  containing  the  naphtha  and  paraffin  scale  is  removed 
and  its  contents  transferred  to  a weighed  platinum  dish.  Some  paraffin 
scale  may  adhere  to  the  Erlenmeyer  flask  in  which  the  precipitation  of 
the  paraffin  scale  was  made,  and  if  necessary  this  flask  is  washed  two 


or  three  times  with  small  amounts  of  naphtha  which  are  transferred 
to  the  platinum  dish  containing  the  naphtha  and  the  paraffin  scale.  The 
naphtha  is  then  evaporated  off  on  the  steam  bath  and  the  platinum  dish 
and  paraffin  scale  are  brought  to  constant  weight  by  heating  for  a few 


29 


minutes  in  an  oven  at  110°C.  The  weight  of  paraffin  scale  divided  by 
the  weight  of  distillate  taken  and  multiplied  by  the  per  cent  of  total 
distillate  in  the  oil  gives  the  per  Cent  of  paraffin  scale  in  the  oil. 

Even  when  performed  under  the  best  conditions,  the  determina- 
tion of  the  paraffin  scale  is  not  accurate,  due  largely  to  the  fact  that 
some  decomposition  takes  place  during  the  distillation  of  the  oil. 
Furthermore,  the  liquid  paraffins  are  probably  just  as  injurious  to  the 
binding  qualities  of  road  oils  as  the  solid  paraffins,  and  the  determina- 
tion of  the  solid  paraffins  appears  to  be,  therefore,  of  small  value,  and 
is  generally  omitted. 

MISCELLANEOUS  TESTS. 

Road  oils  are  sometimes  submitted  also  to  the  following  tests: 
Distillation,  bitumen  removed  by  sulphuric  acid,  bitumen  insoluble  in 
carbon  tetrachloride  and  in  various  other  solvents. 

While  some  of  these  tests  may  give  at  times  valuable  information, 
they  are  not  generally  applied  to  road  oils,  and  the  methods  used  have 
not  been  described  in  this  publication.  Descriptions  of  these  tests 
together  with  discussions  of  some  of  the  special  topics  which  have  been 
taken  up  in  this  bulletin,  may  be  found  in  some  of  the  publications 
listed  below. 

REFERENCES. 

Prof.  Dr.  D.  Holde.  The  Examination  of  Hydrocarbon  Oils,  1915.  John 
Wiley  & Sons,  New  York. 

F.  W.  Clarke.  The  Data  of  Geochemistry,  1916.  Bulletin  616,  United  States 
Geological  Survey,  Department  of  the  Interior,  Washington,  D.  C. 

L.  Ubbelohde.  Handbuch  der  Chemie,  Analyse  und  Technologie  der  Oele  und 
Fette,  1908.  S.  Hirzel,  Leipzig,  Germany. 

Clifford  Richardson.  The  Modern  Asphalt  Pavement,  1914.  John  Wiley  & 
Sons,  New  York. 

Prevost  Hubbard.  Dust  Preventives  & Road  Binders,  1910.  John  Wiley  & 
Sons,  New  York. 

Prevost  Hubbard.  Laboratory  Manual  of  Bituminous  Materials,  1916.  John 
Wiley  & Sons,  New  York. 

Prevost  Hubbard  and  Charles  S.  Reeve.  Methods  for  the  Examination  of 
Bituminous  Road  Materials,  1915.  Bulletin  No.  314,  United  States 
Department  of  Agriculture,  Washington,  D.  C. 

American  Society  for  Testing  Materials,  Year  Book,  1915.  Published  by  the 
Society,  Secretary-Treasurer,  University  of  Pennsylvania,  Philadelphia, 
Pennsylvania. 

American  Society  for  Testing  Materials,  A.  S.  T.  M.  Standards,  1916.  Pub- 
lished by  the  Society,  Secretary-Treasurer,  University  of  Pennsylvania, 
Philadelphia,  Pennsylvania. 


N 


